cmd/link: increase the reserved space for ELF relocations

Currently the offset values of ELF relocations and Macho relocations
are 256 and 512 respectively, which means that the space reserved for
ELF relocations is only 256. But AARCH64 has more than 256 ELF relocation
types, in fact the maximum AARCH64 ELF relocation type recorded in file
src/debug/elf/elf.go is 1032 currently. So this CL increases the offset
of Macho relocations to 2048 to leave enough space for AARCH64 ELF
relocations.

Change-Id: I784ac38aeb3e102ac7825f6d621086849c8d3146
Reviewed-on: https://go-review.googlesource.com/c/go/+/172497
Run-TryBot: Brad Fitzpatrick <bradfitz@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Ian Lance Taylor <iant@golang.org>

src/cmd/internal/objabi/util.go

@@ -34,6 +34,11 @@ var (
 	Version  = version
 )
 
+const (
+	ElfRelocOffset   = 256
+	MachoRelocOffset = 2048 // reserve enough space for ELF relocations
+)
+
 func goarm() int {
 	switch v := envOr("GOARM", defaultGOARM); v {
 	case "5":

src/cmd/link/internal/amd64/asm.go

@@ -103,13 +103,13 @@ func adddynrel(ctxt *ld.Link, s *sym.Symbol, r *sym.Reloc) bool {
 
 	switch r.Type {
 	default:
-		if r.Type >= 256 {
+		if r.Type >= objabi.ElfRelocOffset {
 			ld.Errorf(s, "unexpected relocation type %d (%s)", r.Type, sym.RelocName(ctxt.Arch, r.Type))
 			return false
 		}
 
 		// Handle relocations found in ELF object files.
-	case 256 + objabi.RelocType(elf.R_X86_64_PC32):
+	case objabi.ElfRelocOffset + objabi.RelocType(elf.R_X86_64_PC32):
 		if targ.Type == sym.SDYNIMPORT {
 			ld.Errorf(s, "unexpected R_X86_64_PC32 relocation for dynamic symbol %s", targ.Name)
 		}
@@ -122,7 +122,7 @@ func adddynrel(ctxt *ld.Link, s *sym.Symbol, r *sym.Reloc) bool {
 		r.Add += 4
 		return true
 
-	case 256 + objabi.RelocType(elf.R_X86_64_PC64):
+	case objabi.ElfRelocOffset + objabi.RelocType(elf.R_X86_64_PC64):
 		if targ.Type == sym.SDYNIMPORT {
 			ld.Errorf(s, "unexpected R_X86_64_PC64 relocation for dynamic symbol %s", targ.Name)
 		}
@@ -133,7 +133,7 @@ func adddynrel(ctxt *ld.Link, s *sym.Symbol, r *sym.Reloc) bool {
 		r.Add += 8
 		return true
 
-	case 256 + objabi.RelocType(elf.R_X86_64_PLT32):
+	case objabi.ElfRelocOffset + objabi.RelocType(elf.R_X86_64_PLT32):
 		r.Type = objabi.R_PCREL
 		r.Add += 4
 		if targ.Type == sym.SDYNIMPORT {
@@ -144,7 +144,9 @@ func adddynrel(ctxt *ld.Link, s *sym.Symbol, r *sym.Reloc) bool {
 
 		return true
 
-	case 256 + objabi.RelocType(elf.R_X86_64_GOTPCREL), 256 + objabi.RelocType(elf.R_X86_64_GOTPCRELX), 256 + objabi.RelocType(elf.R_X86_64_REX_GOTPCRELX):
+	case objabi.ElfRelocOffset + objabi.RelocType(elf.R_X86_64_GOTPCREL),
+		objabi.ElfRelocOffset + objabi.RelocType(elf.R_X86_64_GOTPCRELX),
+		objabi.ElfRelocOffset + objabi.RelocType(elf.R_X86_64_REX_GOTPCRELX):
 		if targ.Type != sym.SDYNIMPORT {
 			// have symbol
 			if r.Off >= 2 && s.P[r.Off-2] == 0x8b {
@@ -167,7 +169,7 @@ func adddynrel(ctxt *ld.Link, s *sym.Symbol, r *sym.Reloc) bool {
 		r.Add += int64(targ.Got())
 		return true
 
-	case 256 + objabi.RelocType(elf.R_X86_64_64):
+	case objabi.ElfRelocOffset + objabi.RelocType(elf.R_X86_64_64):
 		if targ.Type == sym.SDYNIMPORT {
 			ld.Errorf(s, "unexpected R_X86_64_64 relocation for dynamic symbol %s", targ.Name)
 		}
@@ -175,9 +177,9 @@ func adddynrel(ctxt *ld.Link, s *sym.Symbol, r *sym.Reloc) bool {
 		return true
 
 	// Handle relocations found in Mach-O object files.
-	case 512 + ld.MACHO_X86_64_RELOC_UNSIGNED*2 + 0,
-		512 + ld.MACHO_X86_64_RELOC_SIGNED*2 + 0,
-		512 + ld.MACHO_X86_64_RELOC_BRANCH*2 + 0:
+	case objabi.MachoRelocOffset + ld.MACHO_X86_64_RELOC_UNSIGNED*2 + 0,
+		objabi.MachoRelocOffset + ld.MACHO_X86_64_RELOC_SIGNED*2 + 0,
+		objabi.MachoRelocOffset + ld.MACHO_X86_64_RELOC_BRANCH*2 + 0:
 		// TODO: What is the difference between all these?
 		r.Type = objabi.R_ADDR
 
@@ -186,7 +188,7 @@ func adddynrel(ctxt *ld.Link, s *sym.Symbol, r *sym.Reloc) bool {
 		}
 		return true
 
-	case 512 + ld.MACHO_X86_64_RELOC_BRANCH*2 + 1:
+	case objabi.MachoRelocOffset + ld.MACHO_X86_64_RELOC_BRANCH*2 + 1:
 		if targ.Type == sym.SDYNIMPORT {
 			addpltsym(ctxt, targ)
 			r.Sym = ctxt.Syms.Lookup(".plt", 0)
@@ -196,11 +198,11 @@ func adddynrel(ctxt *ld.Link, s *sym.Symbol, r *sym.Reloc) bool {
 		}
 		fallthrough
 
-	case 512 + ld.MACHO_X86_64_RELOC_UNSIGNED*2 + 1,
-		512 + ld.MACHO_X86_64_RELOC_SIGNED*2 + 1,
-		512 + ld.MACHO_X86_64_RELOC_SIGNED_1*2 + 1,
-		512 + ld.MACHO_X86_64_RELOC_SIGNED_2*2 + 1,
-		512 + ld.MACHO_X86_64_RELOC_SIGNED_4*2 + 1:
+	case objabi.MachoRelocOffset + ld.MACHO_X86_64_RELOC_UNSIGNED*2 + 1,
+		objabi.MachoRelocOffset + ld.MACHO_X86_64_RELOC_SIGNED*2 + 1,
+		objabi.MachoRelocOffset + ld.MACHO_X86_64_RELOC_SIGNED_1*2 + 1,
+		objabi.MachoRelocOffset + ld.MACHO_X86_64_RELOC_SIGNED_2*2 + 1,
+		objabi.MachoRelocOffset + ld.MACHO_X86_64_RELOC_SIGNED_4*2 + 1:
 		r.Type = objabi.R_PCREL
 
 		if targ.Type == sym.SDYNIMPORT {
@@ -208,7 +210,7 @@ func adddynrel(ctxt *ld.Link, s *sym.Symbol, r *sym.Reloc) bool {
 		}
 		return true
 
-	case 512 + ld.MACHO_X86_64_RELOC_GOT_LOAD*2 + 1:
+	case objabi.MachoRelocOffset + ld.MACHO_X86_64_RELOC_GOT_LOAD*2 + 1:
 		if targ.Type != sym.SDYNIMPORT {
 			// have symbol
 			// turn MOVQ of GOT entry into LEAQ of symbol itself
@@ -223,7 +225,7 @@ func adddynrel(ctxt *ld.Link, s *sym.Symbol, r *sym.Reloc) bool {
 		}
 		fallthrough
 
-	case 512 + ld.MACHO_X86_64_RELOC_GOT*2 + 1:
+	case objabi.MachoRelocOffset + ld.MACHO_X86_64_RELOC_GOT*2 + 1:
 		if targ.Type != sym.SDYNIMPORT {
 			ld.Errorf(s, "unexpected GOT reloc for non-dynamic symbol %s", targ.Name)
 		}
@@ -333,7 +335,7 @@ func adddynrel(ctxt *ld.Link, s *sym.Symbol, r *sym.Reloc) bool {
 				rela.AddUint64(ctxt.Arch, ld.ELF64_R_INFO(uint32(targ.Dynid), uint32(elf.R_X86_64_32)))
 			}
 			rela.AddUint64(ctxt.Arch, uint64(r.Add))
-			r.Type = 256 // ignore during relocsym
+			r.Type = objabi.ElfRelocOffset // ignore during relocsym
 			return true
 		}
 
@@ -359,7 +361,7 @@ func adddynrel(ctxt *ld.Link, s *sym.Symbol, r *sym.Reloc) bool {
 			s.Value = got.Size
 			got.AddUint64(ctxt.Arch, 0)
 			ctxt.Syms.Lookup(".linkedit.got", 0).AddUint32(ctxt.Arch, uint32(targ.Dynid))
-			r.Type = 256 // ignore during relocsym
+			r.Type = objabi.ElfRelocOffset // ignore during relocsym
 			return true
 		}
 	}

src/cmd/link/internal/arm/asm.go

@@ -120,13 +120,13 @@ func adddynrel(ctxt *ld.Link, s *sym.Symbol, r *sym.Reloc) bool {
 
 	switch r.Type {
 	default:
-		if r.Type >= 256 {
+		if r.Type >= objabi.ElfRelocOffset {
 			ld.Errorf(s, "unexpected relocation type %d (%s)", r.Type, sym.RelocName(ctxt.Arch, r.Type))
 			return false
 		}
 
 		// Handle relocations found in ELF object files.
-	case 256 + objabi.RelocType(elf.R_ARM_PLT32):
+	case objabi.ElfRelocOffset + objabi.RelocType(elf.R_ARM_PLT32):
 		r.Type = objabi.R_CALLARM
 
 		if targ.Type == sym.SDYNIMPORT {
@@ -137,11 +137,11 @@ func adddynrel(ctxt *ld.Link, s *sym.Symbol, r *sym.Reloc) bool {
 
 		return true
 
-	case 256 + objabi.RelocType(elf.R_ARM_THM_PC22): // R_ARM_THM_CALL
+	case objabi.ElfRelocOffset + objabi.RelocType(elf.R_ARM_THM_PC22): // R_ARM_THM_CALL
 		ld.Exitf("R_ARM_THM_CALL, are you using -marm?")
 		return false
 
-	case 256 + objabi.RelocType(elf.R_ARM_GOT32): // R_ARM_GOT_BREL
+	case objabi.ElfRelocOffset + objabi.RelocType(elf.R_ARM_GOT32): // R_ARM_GOT_BREL
 		if targ.Type != sym.SDYNIMPORT {
 			addgotsyminternal(ctxt, targ)
 		} else {
@@ -153,7 +153,7 @@ func adddynrel(ctxt *ld.Link, s *sym.Symbol, r *sym.Reloc) bool {
 		r.Add += int64(targ.Got())
 		return true
 
-	case 256 + objabi.RelocType(elf.R_ARM_GOT_PREL): // GOT(nil) + A - nil
+	case objabi.ElfRelocOffset + objabi.RelocType(elf.R_ARM_GOT_PREL): // GOT(nil) + A - nil
 		if targ.Type != sym.SDYNIMPORT {
 			addgotsyminternal(ctxt, targ)
 		} else {
@@ -165,19 +165,19 @@ func adddynrel(ctxt *ld.Link, s *sym.Symbol, r *sym.Reloc) bool {
 		r.Add += int64(targ.Got()) + 4
 		return true
 
-	case 256 + objabi.RelocType(elf.R_ARM_GOTOFF): // R_ARM_GOTOFF32
+	case objabi.ElfRelocOffset + objabi.RelocType(elf.R_ARM_GOTOFF): // R_ARM_GOTOFF32
 		r.Type = objabi.R_GOTOFF
 
 		return true
 
-	case 256 + objabi.RelocType(elf.R_ARM_GOTPC): // R_ARM_BASE_PREL
+	case objabi.ElfRelocOffset + objabi.RelocType(elf.R_ARM_GOTPC): // R_ARM_BASE_PREL
 		r.Type = objabi.R_PCREL
 
 		r.Sym = ctxt.Syms.Lookup(".got", 0)
 		r.Add += 4
 		return true
 
-	case 256 + objabi.RelocType(elf.R_ARM_CALL):
+	case objabi.ElfRelocOffset + objabi.RelocType(elf.R_ARM_CALL):
 		r.Type = objabi.R_CALLARM
 		if targ.Type == sym.SDYNIMPORT {
 			addpltsym(ctxt, targ)
@@ -187,13 +187,13 @@ func adddynrel(ctxt *ld.Link, s *sym.Symbol, r *sym.Reloc) bool {
 
 		return true
 
-	case 256 + objabi.RelocType(elf.R_ARM_REL32): // R_ARM_REL32
+	case objabi.ElfRelocOffset + objabi.RelocType(elf.R_ARM_REL32): // R_ARM_REL32
 		r.Type = objabi.R_PCREL
 
 		r.Add += 4
 		return true
 
-	case 256 + objabi.RelocType(elf.R_ARM_ABS32):
+	case objabi.ElfRelocOffset + objabi.RelocType(elf.R_ARM_ABS32):
 		if targ.Type == sym.SDYNIMPORT {
 			ld.Errorf(s, "unexpected R_ARM_ABS32 relocation for dynamic symbol %s", targ.Name)
 		}
@@ -201,7 +201,7 @@ func adddynrel(ctxt *ld.Link, s *sym.Symbol, r *sym.Reloc) bool {
 		return true
 
 		// we can just ignore this, because we are targeting ARM V5+ anyway
-	case 256 + objabi.RelocType(elf.R_ARM_V4BX):
+	case objabi.ElfRelocOffset + objabi.RelocType(elf.R_ARM_V4BX):
 		if r.Sym != nil {
 			// R_ARM_V4BX is ABS relocation, so this symbol is a dummy symbol, ignore it
 			r.Sym.Type = 0
@@ -210,8 +210,8 @@ func adddynrel(ctxt *ld.Link, s *sym.Symbol, r *sym.Reloc) bool {
 		r.Sym = nil
 		return true
 
-	case 256 + objabi.RelocType(elf.R_ARM_PC24),
-		256 + objabi.RelocType(elf.R_ARM_JUMP24):
+	case objabi.ElfRelocOffset + objabi.RelocType(elf.R_ARM_PC24),
+		objabi.ElfRelocOffset + objabi.RelocType(elf.R_ARM_JUMP24):
 		r.Type = objabi.R_CALLARM
 		if targ.Type == sym.SDYNIMPORT {
 			addpltsym(ctxt, targ)

src/cmd/link/internal/ld/data.go

@@ -162,7 +162,7 @@ func relocsym(ctxt *Link, s *sym.Symbol) {
 			}
 		}
 
-		if r.Type >= 256 {
+		if r.Type >= objabi.ElfRelocOffset {
 			continue
 		}
 		if r.Siz == 0 { // informational relocation - no work to do
@@ -636,7 +636,7 @@ func dynrelocsym(ctxt *Link, s *sym.Symbol) {
 			continue
 		}
 
-		if r.Sym != nil && r.Sym.Type == sym.SDYNIMPORT || r.Type >= 256 {
+		if r.Sym != nil && r.Sym.Type == sym.SDYNIMPORT || r.Type >= objabi.ElfRelocOffset {
 			if r.Sym != nil && !r.Sym.Attr.Reachable() {
 				Errorf(s, "dynamic relocation to unreachable symbol %s", r.Sym.Name)
 			}

src/cmd/link/internal/ld/pe.go

@@ -1401,7 +1401,7 @@ func addPEBaseRelocSym(ctxt *Link, s *sym.Symbol, rt *peBaseRelocTable) {
 		if !r.Sym.Attr.Reachable() {
 			continue
 		}
-		if r.Type >= 256 {
+		if r.Type >= objabi.ElfRelocOffset {
 			continue
 		}
 		if r.Siz == 0 { // informational relocation

src/cmd/link/internal/loadelf/ldelf.go

@@ -923,7 +923,7 @@ func Load(arch *sys.Arch, syms *sym.Symbols, f *bio.Reader, pkg string, length i
 				rp.Sym = elfsym.sym
 			}
 
-			rp.Type = 256 + objabi.RelocType(info)
+			rp.Type = objabi.ElfRelocOffset + objabi.RelocType(info)
 			rp.Siz, err = relSize(arch, pn, uint32(info))
 			if err != nil {
 				return nil, 0, err

src/cmd/link/internal/loadmacho/ldmacho.go

@@ -771,7 +771,7 @@ func Load(arch *sys.Arch, syms *sym.Symbols, f *bio.Reader, pkg string, length i
 							// handle reference to __IMPORT/__pointers.
 							// how much worse can this get?
 							// why are we supporting 386 on the mac anyway?
-							rp.Type = 512 + MACHO_FAKE_GOTPCREL
+							rp.Type = objabi.MachoRelocOffset + MACHO_FAKE_GOTPCREL
 
 							// figure out which pointer this is a reference to.
 							k = int(uint64(ks.res1) + (uint64(rel.value)-ks.addr)/4)
@@ -805,7 +805,7 @@ func Load(arch *sys.Arch, syms *sym.Symbols, f *bio.Reader, pkg string, length i
 			}
 
 			rp.Siz = rel.length
-			rp.Type = 512 + (objabi.RelocType(rel.type_) << 1) + objabi.RelocType(rel.pcrel)
+			rp.Type = objabi.MachoRelocOffset + (objabi.RelocType(rel.type_) << 1) + objabi.RelocType(rel.pcrel)
 			rp.Off = int32(rel.addr)
 
 			// Handle X86_64_RELOC_SIGNED referencing a section (rel->extrn == 0).

src/cmd/link/internal/ppc64/asm.go

@@ -95,7 +95,7 @@ func genplt(ctxt *ld.Link) {
 	for _, s := range ctxt.Textp {
 		for i := range s.R {
 			r := &s.R[i]
-			if r.Type != 256+objabi.RelocType(elf.R_PPC64_REL24) || r.Sym.Type != sym.SDYNIMPORT {
+			if r.Type != objabi.ElfRelocOffset+objabi.RelocType(elf.R_PPC64_REL24) || r.Sym.Type != sym.SDYNIMPORT {
 				continue
 			}
 
@@ -275,13 +275,13 @@ func addelfdynrel(ctxt *ld.Link, s *sym.Symbol, r *sym.Reloc) bool {
 
 	switch r.Type {
 	default:
-		if r.Type >= 256 {
+		if r.Type >= objabi.ElfRelocOffset {
 			ld.Errorf(s, "unexpected relocation type %d (%s)", r.Type, sym.RelocName(ctxt.Arch, r.Type))
 			return false
 		}
 
 		// Handle relocations found in ELF object files.
-	case 256 + objabi.RelocType(elf.R_PPC64_REL24):
+	case objabi.ElfRelocOffset + objabi.RelocType(elf.R_PPC64_REL24):
 		r.Type = objabi.R_CALLPOWER
 
 		// This is a local call, so the caller isn't setting
@@ -298,7 +298,7 @@ func addelfdynrel(ctxt *ld.Link, s *sym.Symbol, r *sym.Reloc) bool {
 
 		return true
 
-	case 256 + objabi.RelocType(elf.R_PPC_REL32):
+	case objabi.ElfRelocOffset + objabi.RelocType(elf.R_PPC_REL32):
 		r.Type = objabi.R_PCREL
 		r.Add += 4
 
@@ -308,7 +308,7 @@ func addelfdynrel(ctxt *ld.Link, s *sym.Symbol, r *sym.Reloc) bool {
 
 		return true
 
-	case 256 + objabi.RelocType(elf.R_PPC64_ADDR64):
+	case objabi.ElfRelocOffset + objabi.RelocType(elf.R_PPC64_ADDR64):
 		r.Type = objabi.R_ADDR
 		if targ.Type == sym.SDYNIMPORT {
 			// These happen in .toc sections
@@ -318,54 +318,54 @@ func addelfdynrel(ctxt *ld.Link, s *sym.Symbol, r *sym.Reloc) bool {
 			rela.AddAddrPlus(ctxt.Arch, s, int64(r.Off))
 			rela.AddUint64(ctxt.Arch, ld.ELF64_R_INFO(uint32(targ.Dynid), uint32(elf.R_PPC64_ADDR64)))
 			rela.AddUint64(ctxt.Arch, uint64(r.Add))
-			r.Type = 256 // ignore during relocsym
+			r.Type = objabi.ElfRelocOffset // ignore during relocsym
 		}
 
 		return true
 
-	case 256 + objabi.RelocType(elf.R_PPC64_TOC16):
+	case objabi.ElfRelocOffset + objabi.RelocType(elf.R_PPC64_TOC16):
 		r.Type = objabi.R_POWER_TOC
 		r.Variant = sym.RV_POWER_LO | sym.RV_CHECK_OVERFLOW
 		return true
 
-	case 256 + objabi.RelocType(elf.R_PPC64_TOC16_LO):
+	case objabi.ElfRelocOffset + objabi.RelocType(elf.R_PPC64_TOC16_LO):
 		r.Type = objabi.R_POWER_TOC
 		r.Variant = sym.RV_POWER_LO
 		return true
 
-	case 256 + objabi.RelocType(elf.R_PPC64_TOC16_HA):
+	case objabi.ElfRelocOffset + objabi.RelocType(elf.R_PPC64_TOC16_HA):
 		r.Type = objabi.R_POWER_TOC
 		r.Variant = sym.RV_POWER_HA | sym.RV_CHECK_OVERFLOW
 		return true
 
-	case 256 + objabi.RelocType(elf.R_PPC64_TOC16_HI):
+	case objabi.ElfRelocOffset + objabi.RelocType(elf.R_PPC64_TOC16_HI):
 		r.Type = objabi.R_POWER_TOC
 		r.Variant = sym.RV_POWER_HI | sym.RV_CHECK_OVERFLOW
 		return true
 
-	case 256 + objabi.RelocType(elf.R_PPC64_TOC16_DS):
+	case objabi.ElfRelocOffset + objabi.RelocType(elf.R_PPC64_TOC16_DS):
 		r.Type = objabi.R_POWER_TOC
 		r.Variant = sym.RV_POWER_DS | sym.RV_CHECK_OVERFLOW
 		return true
 
-	case 256 + objabi.RelocType(elf.R_PPC64_TOC16_LO_DS):
+	case objabi.ElfRelocOffset + objabi.RelocType(elf.R_PPC64_TOC16_LO_DS):
 		r.Type = objabi.R_POWER_TOC
 		r.Variant = sym.RV_POWER_DS
 		return true
 
-	case 256 + objabi.RelocType(elf.R_PPC64_REL16_LO):
+	case objabi.ElfRelocOffset + objabi.RelocType(elf.R_PPC64_REL16_LO):
 		r.Type = objabi.R_PCREL
 		r.Variant = sym.RV_POWER_LO
 		r.Add += 2 // Compensate for relocation size of 2
 		return true
 
-	case 256 + objabi.RelocType(elf.R_PPC64_REL16_HI):
+	case objabi.ElfRelocOffset + objabi.RelocType(elf.R_PPC64_REL16_HI):
 		r.Type = objabi.R_PCREL
 		r.Variant = sym.RV_POWER_HI | sym.RV_CHECK_OVERFLOW
 		r.Add += 2
 		return true
 
-	case 256 + objabi.RelocType(elf.R_PPC64_REL16_HA):
+	case objabi.ElfRelocOffset + objabi.RelocType(elf.R_PPC64_REL16_HA):
 		r.Type = objabi.R_PCREL
 		r.Variant = sym.RV_POWER_HA | sym.RV_CHECK_OVERFLOW
 		r.Add += 2

src/cmd/link/internal/s390x/asm.go

@@ -107,30 +107,30 @@ func adddynrel(ctxt *ld.Link, s *sym.Symbol, r *sym.Reloc) bool {
 
 	switch r.Type {
 	default:
-		if r.Type >= 256 {
+		if r.Type >= objabi.ElfRelocOffset {
 			ld.Errorf(s, "unexpected relocation type %d", r.Type)
 			return false
 		}
 
 		// Handle relocations found in ELF object files.
-	case 256 + objabi.RelocType(elf.R_390_12),
-		256 + objabi.RelocType(elf.R_390_GOT12):
-		ld.Errorf(s, "s390x 12-bit relocations have not been implemented (relocation type %d)", r.Type-256)
+	case objabi.ElfRelocOffset + objabi.RelocType(elf.R_390_12),
+		objabi.ElfRelocOffset + objabi.RelocType(elf.R_390_GOT12):
+		ld.Errorf(s, "s390x 12-bit relocations have not been implemented (relocation type %d)", r.Type-objabi.ElfRelocOffset)
 		return false
 
-	case 256 + objabi.RelocType(elf.R_390_8),
-		256 + objabi.RelocType(elf.R_390_16),
-		256 + objabi.RelocType(elf.R_390_32),
-		256 + objabi.RelocType(elf.R_390_64):
+	case objabi.ElfRelocOffset + objabi.RelocType(elf.R_390_8),
+		objabi.ElfRelocOffset + objabi.RelocType(elf.R_390_16),
+		objabi.ElfRelocOffset + objabi.RelocType(elf.R_390_32),
+		objabi.ElfRelocOffset + objabi.RelocType(elf.R_390_64):
 		if targ.Type == sym.SDYNIMPORT {
 			ld.Errorf(s, "unexpected R_390_nn relocation for dynamic symbol %s", targ.Name)
 		}
 		r.Type = objabi.R_ADDR
 		return true
 
-	case 256 + objabi.RelocType(elf.R_390_PC16),
-		256 + objabi.RelocType(elf.R_390_PC32),
-		256 + objabi.RelocType(elf.R_390_PC64):
+	case objabi.ElfRelocOffset + objabi.RelocType(elf.R_390_PC16),
+		objabi.ElfRelocOffset + objabi.RelocType(elf.R_390_PC32),
+		objabi.ElfRelocOffset + objabi.RelocType(elf.R_390_PC64):
 		if targ.Type == sym.SDYNIMPORT {
 			ld.Errorf(s, "unexpected R_390_PCnn relocation for dynamic symbol %s", targ.Name)
 		}
@@ -143,14 +143,14 @@ func adddynrel(ctxt *ld.Link, s *sym.Symbol, r *sym.Reloc) bool {
 		r.Add += int64(r.Siz)
 		return true
 
-	case 256 + objabi.RelocType(elf.R_390_GOT16),
-		256 + objabi.RelocType(elf.R_390_GOT32),
-		256 + objabi.RelocType(elf.R_390_GOT64):
-		ld.Errorf(s, "unimplemented S390x relocation: %v", r.Type-256)
+	case objabi.ElfRelocOffset + objabi.RelocType(elf.R_390_GOT16),
+		objabi.ElfRelocOffset + objabi.RelocType(elf.R_390_GOT32),
+		objabi.ElfRelocOffset + objabi.RelocType(elf.R_390_GOT64):
+		ld.Errorf(s, "unimplemented S390x relocation: %v", r.Type-objabi.ElfRelocOffset)
 		return true
 
-	case 256 + objabi.RelocType(elf.R_390_PLT16DBL),
-		256 + objabi.RelocType(elf.R_390_PLT32DBL):
+	case objabi.ElfRelocOffset + objabi.RelocType(elf.R_390_PLT16DBL),
+		objabi.ElfRelocOffset + objabi.RelocType(elf.R_390_PLT32DBL):
 		r.Type = objabi.R_PCREL
 		r.Variant = sym.RV_390_DBL
 		r.Add += int64(r.Siz)
@@ -161,8 +161,8 @@ func adddynrel(ctxt *ld.Link, s *sym.Symbol, r *sym.Reloc) bool {
 		}
 		return true
 
-	case 256 + objabi.RelocType(elf.R_390_PLT32),
-		256 + objabi.RelocType(elf.R_390_PLT64):
+	case objabi.ElfRelocOffset + objabi.RelocType(elf.R_390_PLT32),
+		objabi.ElfRelocOffset + objabi.RelocType(elf.R_390_PLT64):
 		r.Type = objabi.R_PCREL
 		r.Add += int64(r.Siz)
 		if targ.Type == sym.SDYNIMPORT {
@@ -172,37 +172,37 @@ func adddynrel(ctxt *ld.Link, s *sym.Symbol, r *sym.Reloc) bool {
 		}
 		return true
 
-	case 256 + objabi.RelocType(elf.R_390_COPY):
-		ld.Errorf(s, "unimplemented S390x relocation: %v", r.Type-256)
+	case objabi.ElfRelocOffset + objabi.RelocType(elf.R_390_COPY):
+		ld.Errorf(s, "unimplemented S390x relocation: %v", r.Type-objabi.ElfRelocOffset)
 		return false
 
-	case 256 + objabi.RelocType(elf.R_390_GLOB_DAT):
-		ld.Errorf(s, "unimplemented S390x relocation: %v", r.Type-256)
+	case objabi.ElfRelocOffset + objabi.RelocType(elf.R_390_GLOB_DAT):
+		ld.Errorf(s, "unimplemented S390x relocation: %v", r.Type-objabi.ElfRelocOffset)
 		return false
 
-	case 256 + objabi.RelocType(elf.R_390_JMP_SLOT):
-		ld.Errorf(s, "unimplemented S390x relocation: %v", r.Type-256)
+	case objabi.ElfRelocOffset + objabi.RelocType(elf.R_390_JMP_SLOT):
+		ld.Errorf(s, "unimplemented S390x relocation: %v", r.Type-objabi.ElfRelocOffset)
 		return false
 
-	case 256 + objabi.RelocType(elf.R_390_RELATIVE):
-		ld.Errorf(s, "unimplemented S390x relocation: %v", r.Type-256)
+	case objabi.ElfRelocOffset + objabi.RelocType(elf.R_390_RELATIVE):
+		ld.Errorf(s, "unimplemented S390x relocation: %v", r.Type-objabi.ElfRelocOffset)
 		return false
 
-	case 256 + objabi.RelocType(elf.R_390_GOTOFF):
+	case objabi.ElfRelocOffset + objabi.RelocType(elf.R_390_GOTOFF):
 		if targ.Type == sym.SDYNIMPORT {
 			ld.Errorf(s, "unexpected R_390_GOTOFF relocation for dynamic symbol %s", targ.Name)
 		}
 		r.Type = objabi.R_GOTOFF
 		return true
 
-	case 256 + objabi.RelocType(elf.R_390_GOTPC):
+	case objabi.ElfRelocOffset + objabi.RelocType(elf.R_390_GOTPC):
 		r.Type = objabi.R_PCREL
 		r.Sym = ctxt.Syms.Lookup(".got", 0)
 		r.Add += int64(r.Siz)
 		return true
 
-	case 256 + objabi.RelocType(elf.R_390_PC16DBL),
-		256 + objabi.RelocType(elf.R_390_PC32DBL):
+	case objabi.ElfRelocOffset + objabi.RelocType(elf.R_390_PC16DBL),
+		objabi.ElfRelocOffset + objabi.RelocType(elf.R_390_PC32DBL):
 		r.Type = objabi.R_PCREL
 		r.Variant = sym.RV_390_DBL
 		r.Add += int64(r.Siz)
@@ -211,14 +211,14 @@ func adddynrel(ctxt *ld.Link, s *sym.Symbol, r *sym.Reloc) bool {
 		}
 		return true
 
-	case 256 + objabi.RelocType(elf.R_390_GOTPCDBL):
+	case objabi.ElfRelocOffset + objabi.RelocType(elf.R_390_GOTPCDBL):
 		r.Type = objabi.R_PCREL
 		r.Variant = sym.RV_390_DBL
 		r.Sym = ctxt.Syms.Lookup(".got", 0)
 		r.Add += int64(r.Siz)
 		return true
 
-	case 256 + objabi.RelocType(elf.R_390_GOTENT):
+	case objabi.ElfRelocOffset + objabi.RelocType(elf.R_390_GOTENT):
 		addgotsym(ctxt, targ)
 
 		r.Type = objabi.R_PCREL

src/cmd/link/internal/sym/reloc.go

@@ -57,8 +57,8 @@ func RelocName(arch *sys.Arch, r objabi.RelocType) string {
 	// Uncomment code when we include those in bootstrap code.
 
 	switch {
-	case r >= 512: // Mach-O
-		// nr := (r - 512)>>1
+	case r >= objabi.MachoRelocOffset: // Mach-O
+		// nr := (r - objabi.MachoRelocOffset)>>1
 		// switch ctxt.Arch.Family {
 		// case sys.AMD64:
 		// 	return macho.RelocTypeX86_64(nr).String()
@@ -71,8 +71,8 @@ func RelocName(arch *sys.Arch, r objabi.RelocType) string {
 		// default:
 		// 	panic("unreachable")
 		// }
-	case r >= 256: // ELF
-		nr := r - 256
+	case r >= objabi.ElfRelocOffset: // ELF
+		nr := r - objabi.ElfRelocOffset
 		switch arch.Family {
 		case sys.AMD64:
 			return elf.R_X86_64(nr).String()

src/cmd/link/internal/x86/asm.go

@@ -172,13 +172,13 @@ func adddynrel(ctxt *ld.Link, s *sym.Symbol, r *sym.Reloc) bool {
 
 	switch r.Type {
 	default:
-		if r.Type >= 256 {
+		if r.Type >= objabi.ElfRelocOffset {
 			ld.Errorf(s, "unexpected relocation type %d (%s)", r.Type, sym.RelocName(ctxt.Arch, r.Type))
 			return false
 		}
 
 		// Handle relocations found in ELF object files.
-	case 256 + objabi.RelocType(elf.R_386_PC32):
+	case objabi.ElfRelocOffset + objabi.RelocType(elf.R_386_PC32):
 		if targ.Type == sym.SDYNIMPORT {
 			ld.Errorf(s, "unexpected R_386_PC32 relocation for dynamic symbol %s", targ.Name)
 		}
@@ -191,7 +191,7 @@ func adddynrel(ctxt *ld.Link, s *sym.Symbol, r *sym.Reloc) bool {
 		r.Add += 4
 		return true
 
-	case 256 + objabi.RelocType(elf.R_386_PLT32):
+	case objabi.ElfRelocOffset + objabi.RelocType(elf.R_386_PLT32):
 		r.Type = objabi.R_PCREL
 		r.Add += 4
 		if targ.Type == sym.SDYNIMPORT {
@@ -202,7 +202,8 @@ func adddynrel(ctxt *ld.Link, s *sym.Symbol, r *sym.Reloc) bool {
 
 		return true
 
-	case 256 + objabi.RelocType(elf.R_386_GOT32), 256 + objabi.RelocType(elf.R_386_GOT32X):
+	case objabi.ElfRelocOffset + objabi.RelocType(elf.R_386_GOT32),
+		objabi.ElfRelocOffset + objabi.RelocType(elf.R_386_GOT32X):
 		if targ.Type != sym.SDYNIMPORT {
 			// have symbol
 			if r.Off >= 2 && s.P[r.Off-2] == 0x8b {
@@ -233,31 +234,31 @@ func adddynrel(ctxt *ld.Link, s *sym.Symbol, r *sym.Reloc) bool {
 		r.Add += int64(targ.Got())
 		return true
 
-	case 256 + objabi.RelocType(elf.R_386_GOTOFF):
+	case objabi.ElfRelocOffset + objabi.RelocType(elf.R_386_GOTOFF):
 		r.Type = objabi.R_GOTOFF
 		return true
 
-	case 256 + objabi.RelocType(elf.R_386_GOTPC):
+	case objabi.ElfRelocOffset + objabi.RelocType(elf.R_386_GOTPC):
 		r.Type = objabi.R_PCREL
 		r.Sym = ctxt.Syms.Lookup(".got", 0)
 		r.Add += 4
 		return true
 
-	case 256 + objabi.RelocType(elf.R_386_32):
+	case objabi.ElfRelocOffset + objabi.RelocType(elf.R_386_32):
 		if targ.Type == sym.SDYNIMPORT {
 			ld.Errorf(s, "unexpected R_386_32 relocation for dynamic symbol %s", targ.Name)
 		}
 		r.Type = objabi.R_ADDR
 		return true
 
-	case 512 + ld.MACHO_GENERIC_RELOC_VANILLA*2 + 0:
+	case objabi.MachoRelocOffset + ld.MACHO_GENERIC_RELOC_VANILLA*2 + 0:
 		r.Type = objabi.R_ADDR
 		if targ.Type == sym.SDYNIMPORT {
 			ld.Errorf(s, "unexpected reloc for dynamic symbol %s", targ.Name)
 		}
 		return true
 
-	case 512 + ld.MACHO_GENERIC_RELOC_VANILLA*2 + 1:
+	case objabi.MachoRelocOffset + ld.MACHO_GENERIC_RELOC_VANILLA*2 + 1:
 		if targ.Type == sym.SDYNIMPORT {
 			addpltsym(ctxt, targ)
 			r.Sym = ctxt.Syms.Lookup(".plt", 0)
@@ -269,7 +270,7 @@ func adddynrel(ctxt *ld.Link, s *sym.Symbol, r *sym.Reloc) bool {
 		r.Type = objabi.R_PCREL
 		return true
 
-	case 512 + ld.MACHO_FAKE_GOTPCREL:
+	case objabi.MachoRelocOffset + ld.MACHO_FAKE_GOTPCREL:
 		if targ.Type != sym.SDYNIMPORT {
 			// have symbol
 			// turn MOVL of GOT entry into LEAL of symbol itself
@@ -342,7 +343,7 @@ func adddynrel(ctxt *ld.Link, s *sym.Symbol, r *sym.Reloc) bool {
 			s.Value = got.Size
 			got.AddUint32(ctxt.Arch, 0)
 			ctxt.Syms.Lookup(".linkedit.got", 0).AddUint32(ctxt.Arch, uint32(targ.Dynid))
-			r.Type = 256 // ignore during relocsym
+			r.Type = objabi.ElfRelocOffset // ignore during relocsym
 			return true
 		}
 	}